Snap-in nut plate

ABSTRACT

A replaceable multiple nut plate, for fastening corrugated or waffle-patterned sheets together, having a plurality of threaded openings for alignment with holes of the sheets and adapted for receiving threaded bolts from one side of the sheets. The nut plate has annular walls, protruding above the openings thereof, for snapping into the holes of the sheets and for allowing the bolts to be screwed into the nut plate without the need for restraining tools.

United States Patent Inventor David L. Buckley Arcadia, Calif. Appl. No.848,233 Filed Aug. 7, 1969 Patented Oct. 12, 1971 Assignee Air LogisticsCorporation Pasadena, Calif.

SNAP-IN NUT PLATE 7 Claims, 3 Drawing Figs.

US. Cl 85/80, 24/204, 52/618, 85/D1G. 2, 287/189.36 F Int. Cl A44b17/00, F16b 13/04, F161) 37/04 Field of Search 85/80, DIG. 2, 32, 32 V,35,17;287/189.36 D, 189.36 F, 189.35; 24/204, 213, 73 HS, 73 MF, 208.1,208 A, 208; 94/13; 244/1 14; l5l/7,69; 52/618, 622, 621

References Cited UNITED STATES PATENTS 9,597 4/1916 Zahner 151/69 UX2,736,248 Gueulich 94/13 3,083,429 4/ 1963 Barlow et al.. 24/208 A3,352,195 11/1967 Fisher 85/80 3,476,165 11/1969 Vaughn 151/69 3,499,6733/1970 Soltysik et a1 ..287/189.36 D X FOREIGN PATENTS 1,111,742 11/1955France 85/P 914,063 12/1962 Great Britain 151/69 Primary Examiner-RamonS. Britts Att0rney-Christie, Parker & l-Iale ABSTRACT: A replaceablemultiple nut plate, for fastening corrugated or waffle-patterned sheetstogether, having a plurality of threaded openings for alignment withholes of the sheets and adapted for receiving threaded bolts from oneside of the sheets. The nut plate has annular walls, protruding abovethe openings thereof, for snapping into the holes of the sheets and forallowing the bolts to be screwed into the nut plate without the need forrestraining tools.

PATENTED um 1 21% liY AT ORNEYS SNAP-IN NUT PLATE BACKGROUND OF THEINVENTION This invention relates to a nut plate and more particularlyconcerns a replaceable fastening strip which can be snapped intoposition underneath the lowermost edge of two or more overlappingsheets.

A variety of structures are presently being constructed in accordancewith fabrication techniques wherein a wall or sheet is fastened to anadjacent wall or sheet by means of bolts, screws, or similar fasteningpins. It is often required that the building materials employed besuitable for installation by a single workman, usually because of theimpossibility or inconvenience of working on both sides of a structure.Simplified construction materials of this type, which can be assembledwith a minimum of manpower and supervision, are obviously of value inthat they allow rapid and low-cost construction.

- A particularly valuable construction technique pertains to theassembly of trackways, landing mats for aircraft, ground cover sheetsand similar assemblies wherein a number of sheets are placed along theground and fastened together at overlapping edges. Corrugated orwaffle-patterned sheets having improved shock resistance and overalldurability are increasingly being utilized as runways for aircraft inareas where a permanent landing surface cannot be readily or feasiblyconstructed. The sheets, which can be rolled into compact shapes fortransportation and installation, ordinarily are placed along -the groundin end-to-end' fashion with the ends overlapping adjacent sheets.Usually constructed of reinforced plastic, they are provided with holesalong their edges for receiving screws or bolts inserted from above theuppermost sheet. An assembly of sheets in this manner can be mostrapidly completed in accordance with a fastening technique which doesnot require utilization of a separate female-threaded portion on theunderside of the lowermost sheet, as this would require restraining ofsuch threaded portion by special tools.

Present methods for fastening one sheet to another call for the moldingor tapping of threaded holes in alternate edges of the sheets to beassembled. Alternately, threaded fittings are permanently fastened tothe lowermost sheet. Fastening devices of these types, however, havebeen particularly disadvantageous in that they establish a top-bottomrelationship that must be adhered to in order to assemble a series ofsheets. Similarly, front-back and left-right relationships are alsodefined using such fastening devices, as when sheets are fastened to oneanother at their sides as well as at their forward and following ends.The sheets must therefore be assorted and assembled such that any oneedge to be fastened corresponds to the appropriate edge of the sheet towhich it is to be fastened, a procedure requiring considerablesupervision and which often results in serious delay in assembly.

STATEMENT OF THE INVENTION In accordance with this invention, two ormore sheets can be fastened together using an elongate strip having aplurality of spaced-apart openings for alignment with holes of thesheets. Means are provided in the strip for receiving fastening pins.Additionally, the strip has means for engaging the sheet against whichit is placed to prevent movement of the strip during insertion of thefastening pins.

Preferably, each of the holes of the strip is threaded and has aprojecting annular wall which can be snapped into the holes of thesheets such that the strip can be secured to an outermost sheet prior toinsertion of the fastening pins. Threaded fastening pins, for example,can then be inserted through the holes of the aligned sheets and screwedinto threaded openings of the strips. The projecting annular wallsprevent pivotal movement of the strip and avoid the need for anyrestraint on such member.

The annular walls of the threaded openings, which define snap-inprojections, have an outer diameter slightly less than that of the holesof the sheets to be fastened. At least two of the openings of thefastening strip are provided with such an annular wall in order toresist pivotal movement of the plate during tightening of the fasteningpins. The thickness of the annular walls, as well as their outerdiameter, allows the strip to be easily snapped into position on a sheetby the simplest of manual operations. That is, a workman need onlyproperly position the strip and exert pressure to cause the walls tosnap into position within the holes of the sheets.

The fastening device of this invention is particularly useful forsecuring together corrugated or waffle-patterned sheets such as thoseemployed in the assembly of trackways, landing mats for aircraft, andthe like. The fastening strip can be constructed of reinforced plasticto conform to the shape of the patterned sheets such that it will takeup a minimum of space both prior to and after assembly of the sheets.Each of the sheets is provided with identically sized and spacedfastener holes along each of their sides such that'they can be assembledin any desired configuration. The sheets are ordinarily transported in arolled-up position and unrolled at the assembly site. The fasteningstrips can be snapped into each of the sheets while they are beingunrolled. Alternately, because of the minimum space required using suchdevices, the sheets can be rolled up with the strips in place, withoutdamage to the sheets or the strips. Damaged strips can be easilyreplaced by prying out the snap-in projections and pressing in areplacement strip.

Although gang" nut plates are'presently utilized in a variety ofconstruction applications, they have failed to provide both low cost andreliable'means for fastening sheets together. For example, conventionalgang channels and the like usually consist of a flat metal strip havinga plurality of nut elements secured thereto. When one of the nutelements is damaged or defective it is required that the entire channelbe replaced, a requirement that could well lead to expensive maintenancecosts wherever a large number of such fastening devices are used.Snap-in, spring-tempered retainers for utilization with removable nutelements have been proposed as a means for allowing a single nut elementto be replaced without having to discard the entire gang strip. Thisapproach, however, represents an undesirable increase in complexity,yielding a fastening device both of high original cost and troublesomeinstallation. In contrast, the fastener of this invention can beconstructed of a low-cost plastic in the simplest possibleconfiguration. It can be easily inserted in a minimum of time and can bediscarded at minimal cost if damaged.

BRIEF DESCRIPTION OF THE DRAWINGS in cross section, fastened togetherusing the fastener shown 1 in FIGS. 1 and 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. I shows a fastening strip2 having four threaded openings 4 for the reception of threaded bolts.Each opening has a projecting annular wall 6 which serves as a snap-inprojection for the fastening strip. The outer diameter of each annularwall is slightly more than the diameter of the holes of the sheets to befastened such that the strip is firmly secured when pressed into asheet. Flexibility of each annular wall is increased by means of fourslots 8 equally spaced around the openings.

FIG. 2 shows the undulating configuration of the fastening strip showsin FIG. 1, such design being adapted for utilization with awaffle-patterned sheet. The projecting annular walls 6 preferably have aheight greater than the thickness of the sheet against which thefastening strip is to be positioned. Each of the annular walls isprovided with an integrally formed lip or flange 10 for further assuringa secure fitting. The lip 10 of each wall 6 contacts the lowermost sheetto prevent the fastening strip from coming loose. A threaded nut element12 integrally formed with the strip is disposed beneath each openmg.

FIG. 3 illustrates the use of the fastening strip of FIGS. 1 and 2 forsecuring two waffle-pattemed sheets 14 and 14' and as reinforced plasticsheets commonly employed in the construction of landing mats foraircraft. The fastening strip 2 is of an undulating configuration suchthat it precisely conforms to the pattern of the sheet. Each of the fourannular walls 6 is snapped into the lowermost sheet by the applicationof pressure on the fastening strip. No further concern need be given tothe fastening strip after it has been so positioned, since the snap-inprojections will hold it securely within the lowermost sheet throughoutthe remaining fastening operations, which are conducted from above theassembly. Hexagonal-head bolts 16 are inserted into the aligned holes 18of the sheets and into the threaded nut element 12 of the fasteningstrip. A washer 20 is usually employed with each bolt to insure a tightfitting. The bolts are then screwed into the nut elements to a positionas shown wherein the head of the bolt is approximately flush with thesurface of the uppermost sheet.

The fastener of this invention is particularly useful for securingtogether corrugated or waffle-patterned sheets constructed of fiberglassor similar reinforced plastic. The strip is preferably constructed ofpolycarbonate although any comparable plastic can be employed. Materialwhich is susceptible to corrosion, however, ordinarily must be coatedwith a protective material.

When employed in an assembly of patterned or corrugated sheets used aslanding mats for aircraft, the fastening strips must normally withstandtorques of approximately 90 inchpounds and impacts such as those createdduring the unrolling of a 48-foot roll of the sheets. That is, thestrips when attached to the sheets prior to assembly must besufficiently durable such that they will not be damaged or loosened whenthe sheets are unrolled and hit the ground. Additionally, each fasteningstrip and bolt combination must normally withstand a shear load of about3,300 pounds. When assembled, the strips may often be placed on mud,sand and the like. Heavy and light vehicles may be driven across themat, which can be used as a landing mat, a roadway and the like. Thestrips must thus be sufficiently durable such that they will not twist,jam or tear loose.

The fastening strips of this invention are easily replaceable since theyrequire no bonding or riveting and are constructed of low-cost plastic.They can be installed in a minimum time and require no special tools. Aworkman can install the strips with gloved hand.

A fastening grip utilized in a landing mat or roadway mat is mostadvantageously utilized in combination with w-inch sized bolts, whichprovide a satisfactory bearing surface.

Smaller bolts can be employed as long as a bearing surface ofapproximately one-half inch diameter is provided.

Although the fastener of this invention has been described in terms of afastening strip having threaded nut elements for use with threadedbolts, it should be noted that alternate fastening pins and strips canbe utilized. For example, the strip can be formed with nut elementsadapted for the locking of an appropriate lock-type fastening pin ratherthan for the screwing of a threaded bolt. In any case, the fastener issecurely held against the lowermost sheet during insertion of thefastening pins.

It is claimed:

1. Apparatus for fastening together a pair of sheets in closely adjacentrelationship, each sheet being of identical wafflepatternedconfiguration and having a plurality of holes defined therethrough, eachhole being aligned with a corresponding hole in the adjacent sheet, theapparatus comprising:

a. an elongate strip of waffle-patterned configuration conforming tothat of the sheets, the strip having a plurality of spaced-apartopenings, each opening adapted for alignment with a distinct pair ofaligned holes in the sheets when the strip is placed against one of thesheets; a plurality of fastening pins each adapted for insertion througha distinct pair of aligned holes in the sheets and into an alignedopening in the elongate strip;

c. means defined on each fastening pin and within the aligned opening inthe elongate strip for securing each pin within the elongate opening;and

d. retaining means projecting from the strip for engaging the sheetagainst which it is placed to prevent movement of the strip relative tothe engaged sheet when the fastening pins are inserted.

2. The apparatus of claim 1, wherein the retaining means comprisesannular walls projecting from the surfaces defining at least two ofelongate strip openings, the walls being engageable with the surfacesdefining holes in at least one sheet.

3. The apparatus of claim 1, wherein the elongate strip openings arethreaded and wherein the fastening pins are threaded bolts.

4. The apparatus of claim 1, wherein the pair of sheets are fastenedtogether in substantially abutting relationship and wherein the strip isplaced in face-to-face contact with one of the sheets.

5. The apparatus of claim 2 wherein the annular walls are slotted.

6. The apparatus of claim 2 wherein the annular walls have a heightgreater than the depth of the surfaces defining the sheet holes, theapparatus further comprising annular flanges extending outwardly fromthe upper ends of the annular walls.

7. Fastener in accordance with claim 1 wherein the strip is formed ofpolycarbonate.

1. Apparatus for fastening together a pair of sheets in closely adjacent relationship, each sheet being of identical wafflepatterned configuration and having a plurality of holes defined therethrough, each hole being aligned with a corresponding hole in the adjacent sheet, the apparatus comprising: a. an elongate strip of waffle-patterned configuration conforming to that of the sheets, the strip having a plurality of spaced-apart openings, each opening adapted for alignment with a distinct pair of aligned holes in the sheets when the strip is placed against one of the sheets; b. a plurality of fastening pins each adapted for insertion through a distinct pair of aligned holes in the sheets and into an aligned opening in the elongate strip; c. means defined on each fastening pin and within the aligned opening in the elongate strip for securing each pin within the elongate opening; and d. retaining means projecting from the strip for engaging the sheet against which it is placed to prevent movement of the strip relative to the engaged sheet when the fastening pins are inserted.
 2. The apparatus of claim 1, wherein the retaining means comprises annular walls projecting from the surfaces defining at least two of elongate strip openings, the walls being engageable with the surfaces defining holes in at least one sheet.
 3. The apparatus of claim 1, wherein the elongate strip openings are threaded and wherein the fastening pins are threaded bolts.
 4. The apparatus of claim 1, wherein the pair of sheets are fastened together in substantially abutting relationship and wherein the strip is placed in face-to-face contact with one of the sheets.
 5. The apparatus of claim 2 wherein the annular walls are slotted.
 6. The apparatus of claim 2 wherein the annular walls have a height greater than the depth of the surfaces defining the sheet holes, the apparatus further comprising annular flanges extending outwardly from the upper ends of the annular walls.
 7. Fastener in accordance with claim 1 wherein the strip is formed of polycarbonate. 